1. Field of the Invention
The present invention relates to a heat sink having a structure, in which flat plate heat radiation fins are mounted on the surface of a base portion, and a fin module to be used in the heat sink.
2. Related Art
As well known in the art, the heat sink is mounted on an object to increase the heat radiation area so as to promote the heat radiation from the object. Therefore, the heat sink may be basically constructed by mounting fin members of a suitable shape on the object in an excellent heat transfer slate. For the general purpose, however, the heat sink has to have a function to joint the fin members to the object. Generally, the heat sink is constructed by integrating the fin members with a base portion of a suitable shape. The base portion in the heat sink having the construction of this kind has no especial function in the heat radiation. In order to raise the heat radiation efficiency or the heat radiation capacity as much as possible, therefore, it is general to mount the heat radiation fins all over the surface of the base portion. An example of this heat sink is disclosed in Japanese Patent Laid-Open No. 11-87961 (JPA11-87961) or 2001-244677 (JPA2001-244677).
In the prior art, moreover, in order to improve the productivity of the heat sink having flat-shaped heat radiation fins, there is known a heat sink which is constructed by folding one metal sheet zigzag to form the heat radiation fin and by mounting the heat radiation fin on the base portion to cover the entire surface of the base portion. The heat radiation fin of this kind is called the xe2x80x9cfolded finxe2x80x9d, which is constructed to have tunnel-shaped air passages and air passages opened upward are formed alternately of each other. This folded fin is used as a heat sink for cooling by forcedly blowing the air in the direction along the face of the heat radiation fin. One example of the heat sink of this kind is exemplified in U.S. Pat. No. 6,288,899.
For the heat sink having the construction in which the numerous fins are erected on the base portion, as disclosed in Japanese Patent Laid-Open No. 11-87961 (JPA11-87961) or 2001-244677 (JPA2001-244677), there is known a structure, in which the fins are mounted on the base portion prepared, or in which the two members are molded integrally with each other. For the former structure having the separate members of the base portion and the fins, these two members have to be integrally jointed. When means using a solder or a soft solder is adopted as the junction structure, however, the thin plate fins cannot retain a sufficient joint area. It is, therefore, difficult to mount the thin plate fins for an enlarged heat radiation area reliably and in a high strength on the base portion.
In order to eliminate this difficulty, there is conceivable a structure, in which grooves are formed in the base portion so that the thin plate fins are fixed by inserting their lower end portions into the grooves. For this structure, however, it is necessary to make the groove width the narrower for the thinner fins. However, the grooves to be molded simultaneously as the base portion is prepared are limited to a width or more. If a cutting method or the like is adopted for forming grooves having small opening widths, not only the number of working steps increases, but also the material yield drops thereby to cause a disadvantage of a low productivity.
On the other hand, the method for manufacturing the fins and the base portion integrally is exemplified by a casing method such as a die-casting method or by an extrusion-molding method. In order to make the fins into the thin plate shape, however, it is necessary to narrow the cavities or molds for the fins. Therefore, the molten metal fails to spread sufficiently into the cavities thereby to cause a casting defect or to break the molds easily. In order to avoid these problems, it is necessary to thick the fins or to lower the fin height with respect to the thickness. As a result, there arises a disadvantage that the fins have a high heat capacity or that a necessary and sufficient heat radiation area cannot be retained.
In the heat sink using the folded fins, on the other hand, these folded fins are jointed at the folded edges to the base portion. It is, therefore, difficult to retain the joint area. Moreover, the individual folded edges of the folded fins are not regularly arrayed on the flat face so that clearances are left between some folded edges and the surface of the base portion. As a result, the heat resistance inbetween may rise to lower the heat radiation characteristics. In the case of the forced air cooling by blowing air downward of the heat sink, moreover, the spaces between the fins have a tunnel shape by half so that they have to be opened upward. There arises another disadvantage that an additional work is required for cutting the folded edges of the folded fins.
The present invention has been conceived in view of the technical problems thus far described and has an object to provide a heat sink having excellent heat radiation characteristics and a satisfactory productivity, and a fin module for the heat sink.
In order to achieve the above-specified object, according to the present invention, there is provided a heat sink comprising: a base portion; and a multiplicity of thin plate fins erected on said base portion in parallel with each other, wherein said fins are folded in two at their lower ends to form two-ply portions and are fixed by having said two-ply portions inserted into grooves formed in said base portion.
In the present invention, therefore, the fins are fixed by inserting the two-ply portions folded thick in two into the grooves formed in the base portion, so that the grooves have a width two times as large as the thickness of the fins. Even if the fins are made of a thin plate shape, therefore, the grooves having the wide opening width can be formed in the base portion. Therefore, the grooves can be formed not by the cutting method but simultaneously with the manufacture time of casting or extrusion-molding the base portion. It is possible to improve the productivity of the base portion and to mount the fins easily on the base portion.
The present invention, portions adjacent to the openings of said grooves are caulked to make excess thicknesses to narrow the opening widths.
In the present invention, therefore, the two-ply portions are not only inserted into the grooves but also clamped by the grooves. Therefore, the mounting strength of the fins on the base portion is raised. As a result, it is possible not only to prevent the fins from coming out in advance but also to lower the heat resistance between the base portion and the fins thereby to improve the heat radiation characteristics as the heat sink.
According to the present invention, said grooves are made wider on their bottom sides than at their openings, and said two-ply portions inserted into said grooves are enlarged in the width direction of said grooves.
In the present invention, therefore, the expanded portions of the two-ply portions in the grooves are retained by the grooves so that the so-called xe2x80x9canchor effect (or anchoring effect)xe2x80x9d is taken to prevent the fins reliably from coming out of the base portion.
According to the present invention, the heat sink further comprises rod-shaped members inserted into said two-ply portions so that said two-ply portions are expanded in the width direction of said grooves.
In the present invention, therefore, the two-ply portions expanded in the grooves take the solid structures, into which the rod-shaped members are inserted. As a result, it is possible to fix the fins more reliably on the base portion.
According to the present invention, the leading end portions of the folded portions forming said two-ply portions are held deeper on the bottom sides than the open ends of said grooves.
In the present invention, therefore, the leading end portions of the folded portions are retained on the inner walls of the grooves. Therefore, the fins do not come out of the grooves so that the strength of mounting the fins on the base portion can be raised.
According to the present invention, said fins are folded generally at a right angle at their upper end portions to form bent members to abut against the adjoining fins. Protrusions are formed at the leading end portions of said bent members, and recesses are so formed at the root end portions of said bent members that they may be jointed to said protrusions of the adjoining fins by fitting said protrusions therein. The fins arrayed in parallel with each other are jointed at their upper end portions by said protrusions and said recesses.
In the present invention, therefore, the bent members formed at the upper end portions of the fins abut against the adjoining fins. In this state, moreover, the protrusions and the recesses engage with each other to joint the upper end portions of the fins. Therefore, the spaces of the fins are kept substantially constant to smoothen the flow of air in the forced cooling case. The fins are regularly arrayed so that the product can give an excellent appearance while preventing its value from dropping.
According to the present invention, said bent members are so formed at the two end portions of said fins other than the widthwise central portions as to form openings in which spaces between the adjoining fins are opened on the upper end sides.
In the present invention, therefore, the bent members formed at the upper end portions of the fins do not cover the entire upper ends of the spaces between the fins, but the spaces are opened upward. By arranging fans while facing the openings, therefore, it is possible to cool the fins forcedly downward.
According to the present invention, moreover, there is provided a heat sink comprising: a base portion; and a multiplicity of thin plate fins erected on said base portion in parallel with each other, wherein said fins are folded generally at a right angle individually at their upper end portions and at their lower end portions to form bent members to abut against the adjoining fins, wherein protrusions are formed at the leading end portions of said bent members, and wherein recesses are so formed at the root end portions of said bent members that they may be jointed to said protrusions of the adjoining fins by fitting said protrusions therein, whereby the fins arrayed in parallel with each other are jointed individually at their upper end portions and at their lower end portions by said protrusions and said recesses.
In the present invention, therefore, the fins arrayed in parallel with each other are held at a constant interval by the bent members formed at their individual two upper and lower end portions, and their individual protrusions are made to engage with the recesses, so that the individual fins are jointed at their two upper and lower end portions. Therefore, the plurality of fins are integrated while being arrayed at the constant interval in parallel with each other. As a result, the fins can be mounted altogether on the base portion.
According to the present invention, said fins jointed by said protrusions and said recesses are mounted on said base portion at their flat face portion formed on the lower end side by said bent members.
In the present invention, the joint area of the fins to the base portion can be enlarged to integrate the fins reliably and firmly with the base portion. Moreover, the heat resistance inbetween can be lowered to improve the heat radiation characteristics as the heat sink.
According to the present invention, moreover, there is provided a fin module comprising a multiplicity of thin plate fins arrayed in parallel with each other, wherein said fins are folded generally at a right angle individually at their upper end portions and at their lower end portions to form bent members to abut against the adjoining fins, wherein protrusions are formed at the leading end portions of said bent members, and wherein recesses are so formed at the root end portions of said bent members that they may be jointed to said protrusions of the adjoining fins by fitting said protrusions therein, whereby the fins arrayed in parallel with each other are jointed individually at their upper end portions and at their lower end portions by said protrusions and said recesses.
In the present invention, therefore, the fins arrayed in parallel with each other are held at the constant interval by the bent members formed at their individual two upper and lower end portions, and the individual protrusions engage with the recesses so that the individual fins are jointed at their two upper and lower end portions. Therefore, the plurality of fins are arrayed and integrated at a constant interval in parallel with each other. The fins can be handled altogether in the integral state.
The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read with reference to the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits to the invention.